If you use the operating system facilities to copy the profile, every character is copied. That includes filters. If transferring a profile to a new computer, these steps work:

https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer

here is the info in brief steps:

1. ensure thunderbird is NOT running on old machine
2. enter %appdata% in search window on task bar and press Enter key
3. this should open windows file explorer in Appdata\roaming folder
4. highlight the Thunderbird folder and copy to external media
5. ensure thunderbird is installed on second computer and NOT running
6. enter %appdata% in search window on task bar and press Enter key
7. you should be in Appdata\roaming folder , copy&paste the exported Thunderbird folder there. This may prompt to overwrite an existing folder of same name. allow it
8. start thunderbird and all should be there

Well, I did everything that you mentioned and I still don't have the filters in the target computer. I did see another post that mentioned the msgFilterRules.dat file, so I checked my target computer. For some reason I have duplicated data in my imapmail folder in the target. The original file has the proper filter data in it, the duplicate doesn't. I'm going to try uninstalling and reinstalling Thunderbird and see if that solves the problem.

Well, that proved fruitless. I deleted the app, restarted, reinstalled and still wind up in the same place, with duplicated data in the imapmail foilder. I'm going to give it one more go of uninstalling, then I'm going to purge the Thunderbird folder from %appdata%/Roaming if it exists and reinstalling. If it fails again I'll find a better email client.

Failed again. I don't have the patience to try and make this work when it should be seamless. I'll find another email client.